Sterilization is a regulatory requirement for medical devices and health-care products. As sterilization is often also performed on foodstuffs, spacecraft materials, mail, pharmaceuticals, and other products, the term “product” will herein be used to refer to any object which is sterilized.
Although many sterilization methods are currently available, exposure to an intense beam of ionizing radiation is becoming increasing popular. This is particularly true in the medical device and pharmaceutical industries. The term “ionizing radiation” refers to any type of radiation that has enough energy to remove electrons from the atoms in a material. Some of the most common types of ionizing radiation are high energy electrons, gamma rays and x-rays.
The physical mechanism behind sterilization with such radiation is inelastic scattering: when the incident particle (e.g. a photon, electron, etc.) interacts with the material in the product, it transfers energy to the product at the location of the interaction. This is quantified in terms of dose, which is calculated as the amount of deposited energy divided by the local mass. Ionizing radiation can also be used for crosslinking of polymers and treatment and neutralization of hazardous waste.
The sterilization of medical devices and health care products by radiation is governed by the International Organization for Standardization (ISO), and is regulated by the ISO 11137 standard. This document specifies that the dose received by the product must be sufficiently high to achieve a sterility assurance level (SAL) of 10-6 (that is, the probability of a non-sterile unit is 1 in 1,000,000). At the same time, the dose must not be so high as to negatively affect the product's functionality. This imposes a narrow range of dose which the product can receive. Similarly, for polymer crosslinking applications, the dose received by the product must be sufficiently high to achieve adequate level of crosslinking but not be so high as to overly harden or embrittle the polymer.
In a typical product design process, testing to ensure that the sterilization regulations are met is only performed after the product has been fully designed, built, tested, and readied for mass production. There is an inherent risk to this approach, namely that a large amount of effort and resources have been invested in a product that may or may not make it to production, depending on the outcome of the sterilization tests.
What is needed is a cost-effective ionizing radiation control system capable of streamlining product design and minimizing redesign due to outcome of testing for sterilization, crosslinking or hazardous waste. Furthermore, the ionizing radiation control system should have speed and performance characteristics allowing for fast processing times.